When we tried the same username and password on gmail.com in Safari, it worked. It also worked logging in to Google Talk using Adium.

So what’s going on? Well, my Google Account is paulschreiber@gmail.com. Most people know Google also accepts emails sent to paul.schreiber@gmail.com. What I didn’t know is that you can also use paul.schreiber as a username. Most of the time.

Let me explain with a chart:

username

gmail.com

iChat

Adium

paulschreiber

YES

YES

YES

paul.schreiber

YES

NO

YES

The problem was the dot. Once we removed it, we could log in successfully.

I assume the same thing happens if your actual username has a dot and you remove it.